This invention relates to a power source system for use in supplying a load with electric power from a plurality of power sources.
As will later be described with reference to several figures of the accompanying drawing, such a conventional power source system comprises a plurality of power sources which are connected either in series or parallel to one another. A load is connected to the power source system through a transmission path, such as a coaxial cable, an optical fiber, or the like and is supplied with a load voltage and a load current from the power source system. The load becomes active when the load voltage and the load current exceed a minimum voltage and a minimum current, respectively. Such a minimum voltage or current will be called a minimum level.
In a series connection of the power sources, the load voltage is substantially equal to a sum of source voltages produced by the respective power sources while the load current is substantially equal to a source current produced by each power source. From this fact, it is understood that the power source share the load at rates of load sharing determined by the source voltages of the respective power sources.
In a parallel connection of the power sources, the load current is substantially equal to a sum of source current produced by the respective power sources while the load voltage is substantially equal to a source voltage produced by each power source. In this event, the source current serve to determine the rates.
In both of the series and the parallel connections of the power sources, it will be noted that selected ones of electric components for determining the rates are called first electric components while the other electric components are called second electric components. At any rate, the second electric components are gradually reduced when the rates become heavy as a result of an increase of the first electric components. This means that each power circuit has a positive resistance characteristic.
It is assumed that one of the power sources interrupts its source voltage and current due to an occurence of a fault and that the rate of the one power source is reduced to zero. The remaining power source should be operated at a maximum rate and must keep either the load current or the load voltage greater than the minimum current or voltage, even on an occurrence of the fault in the one power source. Stated otherwise, the second electric components must be kept at a level greater than the minimum level.
Inasmuch as each power source has a positive resistance characteristic in the manner pointed out hereinabove, the second electric components are reduced to the minimum level when the remaining power source is opeated at the maximum rate. In addition, the load must favorably be put into operation even when the second electric components have the minimum level. This means that the minimum level of the second electric components should be higher than the minimum current or the minimum voltage.
An extra or superfluous electric power should therefore be supplied from the remaining power source to the load in consideration of a fault of the above-mentioned one power source. The superfluous electric power excessively heats the load and requires the load to include a radiator of a big size. This makes the load large in size and expensive.